cairo:operator (cr)

cr -- a cairo:context-t instance
op -- a compositing operator, specified as a cairo:operator-t value

The cairo:operator function gets the current compositing operator for a Cairo context to be used for all drawing operations. The (setf cairo:operator) function sets the compositing operator. See the cairo:operator-t enumeration for details on the semantics of each available compositing operator.

The default operator is the :over value.